A brightness compensation method and device of a display panel

Abstract

The application discloses a brightness compensation method and device of a display panel. The display panel comprises at least a first display area and a second display area. The brightness compensation method of the display panel comprises the following steps: when the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency, determining a first compensation value of the second display area according to a gray scale value of the second display area; determining a correction coefficient according to a display brightness value and the gray scale value of the second display area; correcting the first compensation value according to the correction coefficient; and the first frequency is greater than the second frequency. After the first compensation value corresponding to the display area with a lower refresh frequency is determined, the first compensation value is corrected again according to the correction coefficient, so that the final compensation value of the display area is more accurate, and the brightness compensation of the second display area with a lower refresh frequency is more accurate, the brightness compensation effect is improved, and the problem of display dimming or brightening in some display areas of the display panel during the partition refresh is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a display panel brightness compensation method and device. BACKGROUND

[0002] With the improvement of people's living standards, people are in contact with electronic products all the time, so the demand for display panels is increasing, and display technology has developed rapidly.

[0003] However, with the increase of display demand, there is a problem of display panel partial area display dark or bright in some display scenarios. SUMMARY

[0004] The present application provides a display panel brightness compensation method and device to solve the problem of display panel display dark or bright in some display scenarios.

[0005] According to an aspect of the present application, a display panel brightness compensation method is provided, the display area of the display panel includes at least a first display area and a second display area, and the display panel brightness compensation method includes:

[0006] When the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency:

[0007] According to the gray scale value of the second display area, a first compensation value of the second display area is determined;

[0008] According to the display brightness value and the gray scale value of the second display area, a correction coefficient is determined;

[0009] According to the correction coefficient, the first compensation value is corrected;

[0010] Wherein, the first frequency is greater than the second frequency.

[0011] Optionally, the first compensation value of the second display area is determined according to the gray scale value of the second display area, including:

[0012] According to the gray scale value of the second display area and the corresponding relationship between the gray scale value and the first compensation value of the second display area, the first compensation value of the second display area is determined;

[0013] Optionally, the correction coefficient is determined according to the display brightness value and the gray scale value of the second display area, including:

[0014] According to the display brightness value and the gray scale value of the second display area, and the corresponding relationship between the gray scale value and the correction coefficient under the display brightness value of the second display area, the correction coefficient corresponding to the second display area is determined.

[0015] Optionally, the driving chip corresponding to the display panel comprises a gamma circuit, and the gamma circuit is configured to output a gamma voltage.

[0016] The first compensation value of the second display area is determined according to the gray scale value of the second display area and a corresponding relationship between the gray scale value of the second display area and the first compensation value.

[0017] The first compensation coefficient corresponding to the second display area is determined according to the gray scale value of the second display area and a corresponding relationship between the gray scale value of the second display area and the first compensation coefficient.

[0018] The first compensation value of the second display area is obtained by performing calculation on the first compensation coefficient corresponding to the second display area, a gamma pressure difference value and precision of the gamma circuit, and the gamma pressure difference value is a difference between a maximum value and a minimum value of the gamma voltage output by the gamma circuit.

[0019] Optionally, the first compensation value of the second display area is a product of the first compensation coefficient and a gamma step length, and the gamma step length is a ratio of the gamma pressure difference value to the precision of the gamma circuit.

[0020] Optionally, the first compensation value is corrected according to the correction coefficient, and the correction coefficient is determined according to the display brightness value and the gray scale value of the second display area.

[0021] The product of the correction coefficient and the first compensation value is taken as a corrected compensation value.

[0022] Optionally, the second display area comprises a plurality of display sub-areas, and the first compensation value of the second display area is determined according to the gray scale value of the second display area and a corresponding relationship between the gray scale value of the second display area and the first compensation value.

[0023] For any one of the display sub-areas in the second display area:

[0024] The first compensation coefficient corresponding to the display sub-area is determined according to the gray scale value of the display sub-area and a corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient.

[0025] The first compensation value of the display sub-area is obtained by performing calculation on the first compensation coefficient corresponding to the display sub-area, a gamma pressure difference value and precision of the gamma circuit.

[0026] The correction coefficient is determined according to the display brightness value and the gray scale value of the second display area.

[0027] The correction coefficient is determined according to the display brightness value and the gray scale value of the display sub-area.

[0028] Optionally, before the determining the first compensation coefficient corresponding to the second display area according to the gray scale value of the second display area and the corresponding relationship between the gray scale value of the second display area and the first compensation coefficient, the method further comprises:

[0029] obtaining a first preset compensation table; the first preset compensation table comprises a plurality of binding point gray scale values and a first compensation coefficient corresponding to each display sub-area at each binding point gray scale value;

[0030] for any display sub-area:

[0031] when the gray scale value of the display sub-area is equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined from the first preset compensation table by table lookup;

[0032] when the gray scale value of the display sub-area is not equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined from the first preset compensation table by interpolation.

[0033] Optionally, the determining the correction coefficient corresponding to the second display area according to the display brightness value and the gray scale value of the second display area and the corresponding relationship between the gray scale value under the display brightness value of the second display area and the correction coefficient comprises:

[0034] for any display sub-area:

[0035] the correction coefficient corresponding to the display sub-area is determined according to the display brightness value of the display sub-area and the gray scale value of the display sub-area and the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient; wherein the display brightness values of the display sub-areas are the same;

[0036] before the determining the correction coefficient corresponding to the display sub-area according to the display brightness value of the display sub-area and the gray scale value of the display sub-area and the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient, the method further comprises:

[0037] obtaining a second preset compensation table; the second preset compensation table comprises a plurality of binding point display brightness values, a plurality of binding point gray scale values and a correction coefficient corresponding to the binding point gray scale value under the binding point display brightness value; wherein each display sub-area corresponds to the same second preset compensation table;

[0038] when the gray scale value of the display sub-area is equal to any one of the binding point gray scale values and the display brightness value of the display sub-area is equal to any one of the binding point display brightness values, the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient is determined from the second preset compensation table by table lookup;

[0039] When the gray scale value of the display sub-area is not equal to any one of the binding point gray scale values and / or the display brightness value of the display sub-area is not equal to any one of the binding point display brightness values, a corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient is determined by interpolation according to the second preset compensation table.

[0040] Optionally, in different division manners of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division manners corresponds to the same first preset compensation table.

[0041] Optionally, in different division manners of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division manners corresponds to different first preset compensation tables.

[0042] Before the first compensation coefficient corresponding to the display sub-area is determined according to the gray scale value of the display sub-area and the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient, the method further comprises:

[0043] A plurality of test groups are established, the test groups comprising a binding point first display area and a binding point second display area, the positions of the binding point first display areas being different in different test groups and the positions of the binding point second display areas being different in different test groups.

[0044] A plurality of refresh frequency groups are established, the refresh frequency groups comprising a binding point first frequency and a binding point second frequency.

[0045] For any test group, a binding point compensation table corresponding to the test group under each refresh frequency group is established.

[0046] The test group to which the first display area and the second display area belong is determined according to the positions of the first display area and the second display area in the display panel.

[0047] The first preset compensation table is determined according to the binding point compensation table corresponding to each refresh frequency group under the test group to which the first display area and the second display area belong, the first frequency and the second frequency.

[0048] Optionally, for any test group, establishing the binding point compensation table corresponding to the test group under any refresh frequency group comprises:

[0049] m gray scale values are selected from the plurality of gray scale values as binding point gray scale values; m is an integer greater than or equal to 2.

[0050] The binding point first display area of the test display panel is refreshed at the binding point first frequency, and the binding point second display area of the test display panel is refreshed at the binding point second frequency.

[0051] For any binding point gray scale value:

[0052] lighting the second display area of the binding point with the binding point gray scale value under the preset display brightness value, and collecting actual brightness of each display sub-area in the second display area of the binding point;

[0053] generating a first compensation coefficient of each display sub-area according to the actual brightness of each display sub-area and the target brightness corresponding to the binding point gray scale value under the preset display brightness value;

[0054] generating the binding point compensation table according to the first compensation coefficient corresponding to each binding point gray scale value of each display sub-area.

[0055] Optionally, generating the second preset compensation table comprises:

[0056] selecting h binding point display brightness values from a plurality of display brightness values; h is an integer greater than or equal to 2;

[0057] for any binding point display brightness value of any display sub-area, generating a second compensation coefficient corresponding to the binding point gray scale value under the binding point display brightness value according to the compensated brightness corresponding to the first compensation value and the target brightness corresponding to the binding point gray scale value of the display sub-area under the binding point display brightness value under the binding point gray scale value;

[0058] taking the second compensation coefficient corresponding to any display sub-area satisfying a preset condition as a correction coefficient; the preset condition is that the absolute value of the difference between the first brightness of each display sub-area and the target brightness corresponding to the binding point gray scale value under the binding point display brightness value is less than the absolute value of the difference between the second brightness and the target brightness corresponding to the binding point gray scale value under the binding point display brightness value; the first brightness is the brightness of the display sub-area under the data voltage generated by the first compensation value; the second brightness is the brightness of the display sub-area under the data voltage generated by correcting the first compensation value according to the second compensation coefficient;

[0059] if there is no second compensation coefficient satisfying the preset condition under the binding point gray scale value under the display brightness value, the correction coefficient corresponding to the binding point gray scale value under the display brightness value is set to 1.

[0060] Optionally, before determining the first compensation value of the second display area according to the gray scale value of the second display area, it comprises:

[0061] obtaining the display brightness value of the second display area;

[0062] when the display brightness value is less than a display brightness threshold, determining the first compensation value of the second display area according to the gray scale value of the second display area; wherein the preset display brightness value is less than or equal to the display brightness threshold.

[0063] Optionally, the display panel comprises a gate drive circuit, the gate drive circuit is connected with a clock signal and a frequency division signal; the gate drive circuit is configured to output a scanning signal with a first frequency to the first display area and a scanning signal with a second frequency to the second display area according to the frequency division signal;

[0064] One driving period of the second display area comprises a holding frame and a refreshing frame, in the refreshing frame, the clock signal is controlled to be a pulse signal; in the holding frame, the clock signal is controlled to be an invalid potential; the invalid potential is a potential for turning off a transistor in the gate drive circuit connected with the clock signal; wherein, the invalid potential is a direct current potential.

[0065] Optionally, the display panel comprises a plurality of sub-pixel rows, each sub-pixel row is refreshed row by row, the first display area and the second display area are arranged along the column direction of sub-pixels, and the second display area is refreshed later than the first display area.

[0066] Optionally, after the first compensation value is modified according to the correction coefficient, the method further comprises:

[0067] The brightness of each sub-pixel row in the second display area is compensated according to the modified first compensation value.

[0068] Optionally, the first display area and the second display area are arranged adjacently.

[0069] The brightness of each sub-pixel row in the second display area is compensated from the L+1th sub-pixel row; wherein, the Lth sub-pixel row is the latest refreshed sub-pixel row in the first display area, and L is an integer greater than or equal to 1.

[0070] Optionally, the second display area comprises n sub-pixel rows, and n is an integer greater than or equal to 2; after the first compensation value is modified according to the correction coefficient, the method further comprises:

[0071] The brightness of the L+mth sub-pixel row to the nth sub-pixel row in the second display area of the display panel is compensated according to the modified first compensation value; wherein, the nth sub-pixel row is the latest refreshed sub-pixel row in the second display area, the Lth sub-pixel row is the latest refreshed sub-pixel row in the first display area, m is an integer greater than or equal to 2, L is an integer greater than or equal to 1, and m is less than or equal to n.

[0072] Optionally, the display panel comprises at least a first gate drive circuit for outputting a scanning signal of a first frequency to the first display area and a second gate drive circuit for outputting a scanning signal of a second frequency to the second display area, the first gate drive circuit and the second gate drive circuit being connected to different clock signals.

[0073] One driving period of the second display area comprises a holding frame and a refreshing frame, in the refreshing frame, the clock signal connected to the second gate drive circuit is a pulse signal; in the holding frame, the clock signal connected to the second gate drive circuit is an invalid potential; the invalid potential is a potential for turning off a transistor connected to the clock signal in the gate drive circuit.

[0074] According to another aspect of the present application, there is provided a brightness compensation method for a display panel, the display area of the display panel comprising at least a first display area and a second display area, the display panel further comprising a gate drive circuit, the gate drive circuit being connected to a clock signal and a frequency switching signal; the gate drive circuit being configured to output a scanning signal of a first frequency to the first display area and a scanning signal of a second frequency to the second display area according to the frequency switching signal; wherein the first frequency is greater than the second frequency.

[0075] The brightness compensation method for the display panel comprises:

[0076] According to the display data of the second display area, a display compensation value of the second display area is determined; wherein the display data comprises a gray scale value and / or a display brightness value.

[0077] According to another aspect of the present application, there is provided a brightness compensation device for a display panel, the display area of the display panel comprising at least a first display area and a second display area.

[0078] The brightness compensation device for the display panel comprises:

[0079] A first compensation value generation module is configured to determine a first compensation value according to a gray scale value of the second display area when the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency; wherein the first frequency is greater than the second frequency.

[0080] A correction coefficient generation module is configured to determine a correction coefficient according to a display brightness value and a gray scale value of the second display area.

[0081] A brightness correction module is configured to correct the first compensation value according to the correction coefficient.

[0082] The technical scheme of the embodiment of the present application, when different areas of the display panel are refreshed at different frequencies, determines the first compensation value corresponding to the gray scale value of the display area with a lower refresh frequency according to the gray scale value of the display area with a lower refresh frequency, in order to improve the compensation effect of the display area with a lower refresh frequency, a correction coefficient can be further determined according to the display brightness value and the gray scale value, and the first compensation value is corrected through the correction coefficient. After determining the first compensation value corresponding to the display area with a lower refresh frequency, the first compensation value is corrected again according to the correction coefficient, so that the final compensation value of the display area is more accurate, and the brightness compensation of the second display area with a lower refresh frequency is more accurate, the brightness compensation effect is improved, and the problem of display darkening or brightening in some display areas of the display panel during partition refresh is solved.

[0083] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0084] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0085] Figure 1 A display brightness contrast chart for different display areas of a display panel;

[0086] Figure 2 A flowchart of a brightness compensation method for a display panel provided by an embodiment of the present application;

[0087] Figure 3 A flowchart of another brightness compensation method for a display panel provided by an embodiment of the present application;

[0088] Figure 4 A flowchart of another brightness compensation method for a display panel provided by an embodiment of the present application;

[0089] Figure 5 A display sub-area division chart of a display panel provided by an embodiment of the present application;

[0090] Figure 6 A structural schematic diagram of a display panel provided by an embodiment of the present application;

[0091] Figure 7 A timing diagram of a clock signal provided by an embodiment of the present application;

[0092] Figure 8 A structural schematic diagram of a brightness compensation device of a display panel provided by an embodiment of the present application is shown in FIG. 1.

[0093] Figure 9 A structural schematic diagram of a display device provided by an embodiment of the present application is shown in FIG. 2. DETAILED DESCRIPTION

[0094] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the personnel in the art without creative labor should belong to the scope of protection of the present application.

[0095] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0096] As described in the background, the related display panel has the problem of display panel partial area display dark or bright in some display scenarios. The inventor found that the reason is that when refreshing different display areas of the display panel at different frequencies, the on-off frequency of the transistor for writing data voltage to the pixel circuit in the high refresh area and the low refresh area is different, thereby causing the problem of display brightness dark or bright in the low refresh area. Specifically, the display panel includes a plurality of rows of sub-pixels, the sub-pixels include a pixel circuit and a light emitting device, and the pixel circuit is used to drive the connected light emitting device to emit light. The pixel circuit includes a driving transistor and a data writing transistor, and the data writing transistor is connected with the source or drain of the driving transistor. Taking the connection of the source as an example, when different display areas of the display panel are refreshed at different frequencies, the data writing transistor of the pixel circuit in different display areas turns on different number of times in the same time. In the high refresh area, the number of times that the data writing transistor turns on in one second is greater than the number of times that the data writing transistor in the low refresh area turns on in one second, thereby causing the source of the driving transistor in different display areas to reset different number of times, thereby causing the hysteresis effect of the driving transistor to be different, resulting in the problem of brightness dark or bright in the low refresh area. Exemplarily, Figure 1 A display brightness contrast chart for different display areas of a display panel, Figure 1 Exemplarily shown in the middle, the display panel includes a third display area 3, a first display area 1 and a second display area 2, wherein the third display area 3 and the second display area 2 are refreshed at a frequency of 1HZ, and the first display area 1 is refreshed at a frequency of 120HZ. Because the data writing transistor in the second display area 2 is in the off state most of the time, the brightness dark problem caused by the change in the state of the storage capacitor connected with the driving transistor in the pixel circuit is caused by the frequency reduction measure.

[0097] To solve the above technical problems, the embodiment of the present application provides a display panel brightness compensation method, which determines a first compensation value for the low frequency area when different areas of the display panel are refreshed at different frequencies, solves the problem of display dark or bright in some display areas of the display panel when partition refreshing. At the same time, further correct the first compensation value by the correction coefficient to improve the accuracy of brightness compensation and improve the display effect after compensation.

[0098] Figure 2 The flow chart of the display panel brightness compensation method provided by the embodiment of the present application, the display area of the display panel at least includes a first display area and a second display area, for reference Figure 2 The display panel brightness compensation method includes:

[0099] When the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency:

[0100] S110: determining the first compensation value of the second display area according to the gray scale value of the second display area.

[0101] The display panel includes multiple rows of sub-pixels, and the display panel can be divided into at least a first display area and a second display area in a column direction of the sub-pixel arrangement. The first frequency is greater than the second frequency. For example, the first frequency is 120HZ, and the second frequency is 1HZ. The first display area is refreshed at 120HZ, and the second display area is refreshed at 1HZ. That is, in one second, any sub-pixel in the first display area performs 120 times of data voltage writing, and any sub-pixel in the second display area performs one time of data voltage writing. The display panel has a preset corresponding relationship between the gray scale value and the first compensation value. The corresponding first compensation value can be obtained according to the gray scale value of the second display area.

[0102] Optionally, the first compensation value of the second display area is determined according to the gray scale value of the second display area and the corresponding relationship between the gray scale value and the first compensation value of the second display area.

[0103] The corresponding relationship between multiple gray scale values and first compensation values is established in advance. The first compensation value can be a compensation amount of the gray scale value or a compensation amount of the data voltage, which is not limited in the embodiment. The gray scale value of the second display area can be an average value of the gray scale values of the sub-pixels in the second display area. One driving cycle of the sub-pixel includes a writing frame and a holding frame. In the writing frame, the data voltage is written into the driving transistor in the pixel circuit, and the driving transistor generates a driving current to drive the light emitting device of the sub-pixel to emit light according to the data voltage. In the holding frame, the data voltage is not written into the pixel circuit. Before entering the writing frame of the next driving cycle, the gray scale values of the sub-pixels in the writing frame of the next driving cycle are obtained, and then the average value is obtained as the gray scale value of the second display area according to the gray scale values of the sub-pixels. The corresponding relationship between the gray scale value and the first compensation value of the second display area is determined by searching or interpolation from the corresponding relationship between multiple gray scale values and first compensation values established in advance, and then the corresponding first compensation value is obtained according to the gray scale value of the second display area in the next driving cycle.

[0104] S120: determining the correction coefficient according to the display brightness value and the gray scale value of the second display area.

[0105] The display device such as mobile phone and computer usually includes a brightness adjustment button, and the user changes the input display brightness level (Display Brightness Value, DBV) through the brightness adjustment button. Each display brightness value corresponds to a display brightness of the maximum gray scale of the display panel. When the display brightness corresponding to the maximum gray scale of the display panel changes, the display brightness corresponding to other gray scales also changes. Specifically, when the display brightness corresponding to the maximum gray scale of the display panel increases, the display brightness corresponding to other gray scales also increases; when the display brightness corresponding to the maximum gray scale of the display panel decreases, the display brightness corresponding to other gray scales also decreases. Therefore, it can also be understood that each input display brightness value corresponds to a brightness level of the display panel. When the display brightness corresponding to the maximum gray scale of the display panel is larger, the brightness level is larger, and the overall display brightness of the display panel is larger; when the display brightness corresponding to the maximum gray scale of the display panel is smaller, the brightness level is smaller, and the overall display brightness of the display panel is smaller.

[0106] The display brightness value DBV and the gray scale value of the second display area in the next driving period can be regarded as a group of display parameters, and the group of display parameters corresponds to the correction coefficient. After the display brightness value and the gray scale value of the second display area in the next driving period are determined, the corresponding correction coefficient can be obtained. Alternatively, according to the display brightness value and the gray scale value of the second display area, and the corresponding relationship between the gray scale value under the display brightness value of the second display area and the correction coefficient, the correction coefficient corresponding to the second display area is determined. The display brightness value and the gray scale value are regarded as a group of display parameters, and the corresponding relationship between a plurality of groups of display parameters and correction coefficients is established in advance. The corresponding relationship between the display parameters and the correction coefficient of the second display area in the next driving period is determined by table lookup or interpolation from the plurality of corresponding relationships, and then the correction coefficient corresponding to the second display area is determined.

[0107] S130: correcting the first compensation value according to the correction coefficient.

[0108] The first compensation value is corrected according to the correction coefficient, that is, the final compensation value is obtained by operating the correction coefficient and the first compensation value. In order to simplify the calculation process and the occupation of storage space, the same first compensation value can be used for each sub-pixel in the second display area. Further, for any sub-pixel in the second display area, a final compensated data voltage is generated according to the final compensation value, so as to drive the sub-pixel to display, and the brightness compensation of the second display area is realized. Taking the compensation amount of the first compensation value as the data voltage as an example, the final compensation value is obtained by operating the correction coefficient and the first compensation value. For any sub-pixel in the second display area, the final compensated data voltage is generated according to the sum of the initial data voltage of the sub-pixel in the next driving cycle and the final compensation value, and the light emitting device in the sub-pixel is driven to display by using the final compensated data voltage in the next driving cycle, so as to complete the brightness compensation of each sub-pixel in the second display area.

[0109] The technical scheme of the embodiment of the present application, when different regions of the display panel are refreshed at different frequencies, determines the first compensation value corresponding to the display area at the gray scale value according to the gray scale value of the display area with lower refresh frequency. In order to improve the compensation effect of the display area with lower refresh frequency, the correction coefficient can be further determined according to the display brightness value and the gray scale value, and the first compensation value is corrected by the correction coefficient. After the first compensation value corresponding to the display area with lower refresh frequency is determined, the first compensation value is corrected again according to the correction coefficient, so that the final compensation value of the display area is more accurate, and the brightness compensation of the second display area with lower refresh frequency is more accurate, the brightness compensation effect is improved, and the problem of display darkening or brightening in some display areas of the display panel during partition refresh is solved.

[0110] Figure 3 The flowchart of another brightness compensation method of a display panel provided by the embodiment of the present application, the driving chip corresponding to the display panel includes a gamma circuit, the gamma circuit is used for outputting a gamma voltage, the display device formed by the display panel includes the driving chip, the driving chip is arranged corresponding to the display panel of the display device, and the brightness compensation method of the display panel includes Figure 3 , the brightness compensation method of the display panel includes:

[0111] S111: determining the first compensation coefficient corresponding to the second display area according to the gray scale value of the second display area and the corresponding relationship between the gray scale value of the second display area and the first compensation coefficient.

[0112] The first compensation coefficient is an integer, and the maximum value and the minimum value of the first compensation coefficient are opposite numbers, and the maximum value and the minimum value are related to the related setting of the driving chip.

[0113] The gray scale value of the display panel corresponds to the first compensation coefficient, one gray scale value corresponds to one first compensation coefficient, the corresponding relationship between the plurality of gray scale values and the first compensation coefficients under the preset display brightness value can be established in advance, and then according to the plurality of corresponding relationships between the plurality of gray scale values and the first compensation coefficients, the corresponding relationship between the gray scale value of the second display area and the first compensation coefficient can be determined by searching or interpolation, and then the first compensation coefficient corresponding to the gray scale value of the second display area is obtained. When determining the first compensation coefficient, the size of the display brightness value of the writing frame of the second display area in the next driving period is not considered, and only the size of the gray scale value of the second display area is considered to determine the corresponding first compensation coefficient. That is, no matter at which display brightness value, the first compensation coefficient corresponding to the gray scale value of the second display area in the next driving period is determined according to the relationship between the gray scale value and the first compensation coefficient established under the preset display brightness value.

[0114] S121: The first compensation value of the second display area is obtained by operating the first compensation coefficient corresponding to the second display area, the gamma pressure difference value and the accuracy of the gamma circuit; the gamma pressure difference value is the difference between the maximum value of the gamma voltage output by the gamma circuit and the minimum value of the gamma voltage.

[0115] The gamma voltage corresponds to the data voltage one by one, the minimum unit of the gamma voltage output can be obtained according to the gamma pressure difference value and the accuracy of the gamma circuit, the first compensation coefficient can represent the share of the voltage, and then the first compensation value can be obtained according to the first compensation coefficient and the minimum unit of the gamma voltage output. The first compensation value is the compensation amount of the data voltage. Optionally, the first compensation value of the second display area is the product of the first compensation coefficient and the gamma step length, the gamma step length is the ratio of the gamma pressure difference value to the accuracy of the gamma circuit, and the gamma step length is the minimum unit of the gamma voltage output.

[0116] S131: According to the display brightness value and the gray scale value of the second display area, and the corresponding relationship between the gray scale value and the correction coefficient under the display brightness value of the second display area, the correction coefficient corresponding to the second display area is determined.

[0117] No matter at which display brightness value, the first compensation coefficient corresponding to the gray scale value of the second display area in the next driving period is determined according to the relationship between the gray scale value and the first compensation coefficient established under the preset display brightness value. Therefore, the accuracy of the first compensation value obtained according to the first compensation coefficient is not high, and further correction is needed.

[0118] A third preset compensation table is established in advance, the third preset compensation table includes a plurality of binding point display brightness values, a plurality of binding point gray scale values, and a correction coefficient corresponding to the binding point gray scale value under the binding point display brightness value.

[0119] When the gray scale value of the second display area is equal to any one of the binding point gray scale values and the display brightness value of the second display area is equal to any one of the binding point display brightness values, the corresponding relationship between the gray scale value and the correction coefficient of the second display area at the display brightness value of the write-in frame of the next driving period is determined from the third preset compensation table by means of table lookup;

[0120] When the gray scale value of the second display area in the write-in frame of the next driving period is not equal to any one of the binding point gray scale values and / or the display brightness value of the second display area is not equal to any one of the binding point display brightness values, the corresponding relationship between the gray scale value and the correction coefficient of the second display area at the display brightness value is determined by means of interpolation according to the third preset compensation table, and then the correction coefficient corresponding to the second display area is determined.

[0121] S141: correcting the first compensation value according to the correction coefficient.

[0122] The product of the correction coefficient and the first compensation value is taken as the corrected compensation value.

[0123] In the embodiment, the first compensation value of the second display area is obtained by performing operations according to the first compensation coefficient corresponding to the second display area, the gamma pressure difference value and the precision of the gamma circuit, and the first compensation value is corrected by the correction coefficient, so that the brightness compensation of the second display area with a lower refresh frequency is more accurate, and the brightness compensation effect is improved.

[0124] Figure 4 A flowchart of another brightness compensation method of a display panel provided by the embodiment of the present application, Figure 5 A display sub-area division diagram of a display panel provided by the embodiment of the present application, the second display area includes a plurality of display sub-areas, for reference Figure 4 and Figure 5 Optionally, for any display sub-area in the second display area, the brightness compensation method of the display panel includes:

[0125] S112: obtaining a first preset compensation table. The first preset compensation table includes a plurality of binding point gray scale values and a first compensation coefficient corresponding to each display sub-area at each binding point gray scale value.

[0126] The second display area of the display panel can be divided into a plurality of display sub-areas according to the row direction and / or column direction of the sub-pixels in the display panel, and in the embodiment, the second display area 2 is exemplarily divided into a first display sub-area ① to a sixteenth display sub-area There are sixteen display sub-areas. The brightness compensation of the second display area 2 is performed on all display sub-areas respectively, and the brightness compensation of the first display sub-area ① is taken as an example.

[0127] Before the display panel is shipped, the first preset compensation table can be established by testing the display panel multiple times. The first preset compensation table is stored in the memory of the display panel to be compensated.

[0128] Table 1: first preset compensation table

[0129]

[0130] For example, the gray scale value in the display panel ranges from 0 to 255. In the first preset compensation table, the gray scale conversion amount divided by 16 represents the size of the gray scale value of the binding point. In other embodiments, the gray scale value of the binding point can also be directly indicated in the first column of the table. The 0, 1, 2, and 3 in the first row of Table 1 represent the gray scale values of the first, second, third, and fourth binding points, respectively. Figure 5 The first, second, third, and fourth columns of the second display area 2 shown in the second display area 2 are shown in the second display area 2. As can be seen from Table 1, the first compensation coefficients of the first display sub-area ① to the sixteenth display sub-area ⑩ are shown when the gray scale values of the binding points are 0, 8, 16, and 32. For the convenience of displaying the table, only four gray scale values of the binding points are shown, and the actual number of gray scale values of the binding points is not limited to four.

[0131] ​For a group of refresh frequency groups, the refresh frequency group includes the refresh frequency of the first display area and the refresh frequency of the second display area, and only one first preset compensation table corresponding to the display panel to be compensated can be stored in the memory. That is, in the process of establishing the first preset compensation table in the early stage, the first preset compensation table is established by testing the position division of the first display area and the second display area of the display panel only once, and subsequently, although the position division of the first display area and the second display area of the display panel to be compensated is different from that of the tested display panel, the first compensation value is still determined by referring to the first preset compensation table, so as to save the occupation of the chip space. With the progress of picture display, the position division of the high refresh area and the low refresh area may change, that is, the position division of the first display area and the second display area may change, and the second display area in different positions all refers to the same first preset compensation table to determine the first compensation value, that is, under different division modes of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division modes corresponds to the same first preset compensation table, and the early generation of a first preset compensation table can reduce the early workload and reduce the occupation of the storage space by the first preset compensation table. Among them, the first display area and the second display area correspond to different display area boundaries in different division modes. For example, in one division mode, the first display area is the 1st row of sub-pixel row to the 50th row of sub-pixel row, and the second display area is the 51st row of sub-pixel row to the 100th row of sub-pixel row, and in another division mode, the first display area is the 1st row of sub-pixel row to the 30th row of sub-pixel row, and the second display area is the 31st row of sub-pixel row to the 100th row of sub-pixel row, and the second display area corresponding to the two division modes corresponds to the same first preset compensation table when compensation is performed.

[0132] Alternatively, under different division modes of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division modes corresponds to different first preset compensation tables. For a group of refresh frequency groups, when establishing the first preset compensation table in the early stage, the position division of the first display area and the second display area is changed constantly, and a first preset compensation table is established every time the division mode is changed, so that in actual compensation, the first compensation value is determined according to the first preset compensation table corresponding to the position division of the tested display panel which is closest to the position division of the second display area of the display panel to be compensated under the current working condition. The second display area corresponding to different division modes corresponds to different first preset compensation tables, which is beneficial to improve the accuracy of subsequent compensation. Specifically:

[0133] A plurality of test groups are established, the test groups including positions of the first display area and the second display area of the binding point, the positions of the first display area of the binding point being different in different test groups, and the positions of the second display area of the binding point being different; a plurality of refresh frequency groups are established, the refresh frequency groups including the first frequency of the binding point and the second frequency of the binding point; wherein the first frequency of the binding point is the refresh frequency of the first display area of the binding point, and the second frequency of the binding point is the refresh frequency of the second display area of the binding point. For any test group, a corresponding binding point compensation table of the test group under each refresh frequency group is established; the test group to which the first display area and the second display area belong is determined according to the positions of the first display area and the second display area in the display panel; and the first preset compensation table is determined according to the binding point compensation table corresponding to each refresh frequency group under the test group to which the first display area and the second display area belong, the first frequency and the second frequency.

[0134] For example, the test display panel includes 100 rows and 100 columns of sub-pixels, and the first display area of the binding point in the first test group of the plurality of test groups established by taking the column direction of the sub-pixels as an example corresponds to a region from the 50th row to the 70th row, and the second display area of the binding point corresponds to a region from the 71st row to the 100th row; the first display area of the binding point in the second test group corresponds to a region from the 30th row to the 50th row, and the second display area of the binding point corresponds to a region from the 51st row to the 70th row, and so on. Different test groups are established according to different positions. Different refresh frequency groups are established, and the refresh frequency groups include the refresh frequency of the first display area of the binding point and the refresh frequency of the second display area of the binding point, such as three groups of refresh frequencies, the first group being 120HZ and 1HZ, the second group being 120HZ and 60HZ, and the third group being 200HZ and 1HZ. For any test group, three binding point preset compensation tables are established under the above three groups of refresh frequency groups. First, the test group to which the second display area of the display panel to be compensated belongs is determined according to the position of the second display area of the display panel to be compensated, and specifically, the test group corresponding to the binding point second display area with the most overlapping rows of the second display area of the binding point in the test group can be taken as the test group to which the second display area belongs. After determining the test group to which the second display area belongs, if the group composed of the first frequency and the second frequency is the same as one of the plurality of refresh frequency groups, the binding point compensation table corresponding to the test group in the refresh frequency group is directly taken as the first preset compensation table; otherwise, the compensation table corresponding to the test group under the group composed of the first frequency and the second frequency is determined by interpolation, and the compensation table is taken as the first preset compensation table.

[0135] Further, for any test group, the corresponding binding point compensation table of the test group under any refresh frequency group includes:

[0136] m gray scale values are selected from the plurality of gray scale values as the binding point gray scale values; m is an integer greater than or equal to 2; the first display area of the binding point is refreshed at the first frequency of the binding point, and the second display area of the binding point is refreshed at the second frequency of the binding point;

[0137] for any one of the binding point gray scale values:

[0138] lighting the second display area of the binding point with the binding point gray scale value under the preset display brightness value, and collecting the actual brightness of each display sub-area in the second display area of the binding point;

[0139] According to the actual brightness of each display sub-area and the target brightness corresponding to the binding point gray scale value under the preset display brightness value, a first compensation coefficient of each display sub-area is generated.

[0140] According to the first compensation coefficient corresponding to each display sub-area under each binding point gray scale value, a binding point compensation table is generated.

[0141] For example, the binding point gray scale value can be 0, 8, 16, 32, etc. The preset display brightness value can be set by the user according to the user's needs, such as the brightness corresponding to the maximum gray scale under the preset display brightness value is 2nit. After lighting the second display area of the binding point with the binding point gray scale value under the preset display brightness value, for any display sub-area, the sum of the brightness of each sub-pixel in the display sub-area can be obtained by a camera or other brightness acquisition device, and it is taken as the actual brightness of the display sub-area. The preset display brightness value corresponds to a gamma curve, which is used to represent the one-to-one correspondence between display brightness value and gray scale value. For any sub-pixel, the brightness corresponding to the binding point gray scale value on the gamma curve corresponding to the preset display brightness value is taken as the target brightness of the sub-pixel, and the sum of the target brightness of each sub-pixel in the display sub-area is taken as the target brightness of the display sub-area. For any display sub-area, the first compensation coefficient is generated according to the difference between the actual brightness and the target brightness, and then the first compensation coefficient corresponding to each display sub-area under each binding point gray scale value constitutes the binding point compensation table.

[0142] S122: When the gray scale value of the display sub-area is equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined from the first preset compensation table by table lookup; when the gray scale value of the display sub-area is not equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined according to the first preset compensation table and by interpolation.

[0143] Specifically, when the gray scale value of the display sub-area is equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is equal to the corresponding relationship between the binding point gray scale value and the first compensation coefficient corresponding to the binding point gray scale value in the first preset compensation table. For example, taking the first display sub-area ① as an example, when the gray scale value of the first display sub-area ① is equal to 8, the first compensation coefficient corresponding to the first display sub-area ① under the binding point gray scale value of 8 is directly obtained from the first preset compensation table by table lookup.

[0144] If the gray scale value of the first display sub-area ① is 20, the first compensation coefficient corresponding to the gray scale value of 16 of the binding point and the first compensation coefficient corresponding to the gray scale value of 32 of the binding point of the first display area ① are used to determine the first compensation coefficient corresponding to the gray scale value of 20 of the first display area ① by interpolation, that is, the corresponding relationship between the gray scale value and the first compensation coefficient of the first display sub-area ① is determined. The difference value can be linear interpolation.

[0145] S132: determining the first compensation coefficient corresponding to the display sub-area according to the gray scale value of the display sub-area and the corresponding relationship between the gray scale value and the first compensation coefficient of the display sub-area.

[0146] The average value of the gray scale values of all sub-pixels in the display sub-area in the next driving period is written as the gray scale value of the display sub-area, the corresponding relationship between the gray scale value and the first compensation coefficient of the display sub-area is determined according to steps S112-S122, and the first compensation coefficient is determined after the corresponding relationship is determined. Taking the first display sub-area ① as an example, the average value of the gray scale values of all sub-pixels in the first display sub-area ① in the next driving period is written as the gray scale value of the first display sub-area ①. The corresponding relationship between the gray scale value and the first compensation coefficient of the first display sub-area ① is determined according to steps S112-S122, and the first compensation coefficient corresponding to the first display sub-area ① is determined. The determination process of the first compensation coefficient corresponding to other display sub-areas is similar to the above, and will not be described in detail. The gray scale value of the display sub-area in each step represents the gray scale value corresponding to the display sub-area in the next driving period, and specifically, the gray scale value of the display sub-area is the average value of the gray scale values of all sub-pixels in the display sub-area in the next driving period.

[0147] S142: calculating the first compensation value of the display sub-area by operating the first compensation coefficient corresponding to the display sub-area, the gamma step value and the accuracy of the gamma circuit.

[0148] For any display sub-area, the first compensation value thereof is equal to the product of the first compensation coefficient corresponding to the display sub-area ① and the gamma step value. Taking the first display sub-area ① as an example, the first compensation value thereof is equal to the product of the first compensation coefficient corresponding to the first display sub-area ① and the gamma step value.

[0149] S152: obtaining a second preset compensation table; the second preset compensation table includes a plurality of binding point display brightness values, a plurality of binding point gray scale values and a correction coefficient corresponding to the binding point gray scale value under the binding point display brightness value; wherein each display sub-area corresponds to the same second preset compensation table.

[0150] The second preset compensation table is established in advance, and the second preset compensation table is stored in the memory before the display panel to be compensated is shipped. The second preset compensation table shown in Table 2 is as follows: the gray scale conversion amount in the first column is the same as that in Table 1, the gray scale conversion amount divided by 16 represents the gray scale value of the binding point, 0 in the first row represents the display brightness value of the maximum gray scale corresponding to the brightness of 0, 1 represents the display brightness value of the maximum gray scale corresponding to the brightness of 1 nit, 204 represents the display brightness value of the maximum gray scale corresponding to the brightness of 5 nit, 342 represents the display brightness value of the maximum gray scale corresponding to the brightness of 10 nit, 660 represents the display brightness value of the maximum gray scale corresponding to the brightness of 30 nit, 1204 represents the display brightness value of the maximum gray scale corresponding to the brightness of 89.8 nit, and the value of any cell in the table except the first row and the first column is divided by 128 to represent the correction coefficient. Alternatively, the rows of the second preset compensation table can be directly different binding point display brightness values, and the columns can be binding point gray scale values such as 0 gray scale, 8 gray scale, 16 gray scale, 32 gray scale, etc. The value of any cell except the first row and the first column is a correction coefficient, which is not specifically limited in the embodiment. Due to the limitation of the bit of the driving chip, the value of the cell in Table 2 except the first row and the first column is less than or equal to 1024 in the embodiment.

[0151] Table 2: Second preset compensation table

[0152] Gray scale conversion amount 0 1 204 342 660 1204 0 0 0 0 0 0 0 128 0 200 128 140 110 64 256 0 160 160 150 120 50 512 0 250 240 190 120 50

[0153] Further, generating the second preset compensation table comprises:

[0154] selecting h binding point display brightness values from the plurality of display brightness values; h is an integer greater than or equal to 2;

[0155] for any binding point display brightness value of any display sub-area, generating a second compensation coefficient corresponding to the binding point gray scale value under the binding point display brightness value according to the compensated brightness corresponding to the first compensation value and the target brightness corresponding to the binding point gray scale value of the display sub-area under the binding point display brightness value.

[0156] generating a coarsely adjusted data voltage according to the first compensation value, driving the display sub-area to display according to the coarsely adjusted data voltage, and further obtaining a brightness compensated according to the coarsely adjusted value. Further, the second compensation coefficient is generated according to the difference between the compensated brightness corresponding to the first compensation value and the target brightness corresponding to the binding point gray scale value of the display sub-area under the binding point display brightness value, so as to correct the brightness compensated according to the coarsely adjusted value, so as to make it closer to the target brightness.

[0157] The second compensation coefficient corresponding to any one display sub-area meeting the preset condition is taken as the correction coefficient; the preset condition is that the absolute value of the difference between the first brightness of each display sub-area and the target brightness corresponding to the bind point gray scale value of the display sub-area at the bind point display brightness value is less than the absolute value of the difference between the second brightness and the target brightness corresponding to the bind point gray scale value at the bind point display brightness value; the first brightness is the brightness of the display sub-area lighting at the data voltage generated by the first compensation value; the second brightness is the brightness of the display sub-area lighting at the data voltage generated by correcting the first compensation value according to the second compensation coefficient;

[0158] If there is no second compensation coefficient meeting the preset condition at the bind point gray scale value at the display brightness value, the correction coefficient corresponding to the bind point gray scale value at the display brightness value is set to 1.

[0159] Since each display sub-area corresponds to the same correction coefficient at a certain bind point gray scale value at a certain bind point display brightness value, if the brightness of each display sub-area lighting at the data voltage generated by correcting the first compensation value according to the correction coefficient cannot meet the target brightness, no correction is performed, so that when the brightness of some display sub-areas is closer to the target brightness, the display effect of the remaining display sub-areas is not further improved or even worse than the display effect compensated by the first compensation value.

[0160] S162: When the gray scale value of the display sub-area is equal to any one bind point gray scale value and the display brightness value of the display sub-area is equal to any one bind point display brightness value, the corresponding relationship between the gray scale value at the display brightness value of the display sub-area and the correction coefficient is determined from the second preset compensation table by table lookup; when the gray scale value of the display sub-area is not equal to any one bind point gray scale value and / or the display brightness value of the display sub-area is not equal to any one bind point display brightness value, the corresponding relationship between the gray scale value at the display brightness value of the display sub-area and the correction coefficient is determined from the second preset compensation table by interpolation.

[0161] Specifically, when the gray scale value of the display sub-area is equal to one of the multiple bind point gray scale values in the second preset compensation table and the display brightness value of the display sub-area is equal to one of the multiple bind point display brightness values, the corresponding relationship between the gray scale value at the display brightness value of the display sub-area and the correction coefficient is equal to the corresponding relationship between the bind point gray scale value at the bind point display brightness value and the correction coefficient corresponding to the bind point gray scale value at the bind point display brightness value in the second preset compensation table. For example, taking the first display sub-area ① as an example, when the gray scale value of the first display sub-area ① is equal to 8 and the conversion amount corresponding to the display brightness value is 204, the correction coefficient of the first display sub-area ① is directly obtained from the second preset compensation table by table lookup, which is 128 / 128=1.

[0162] If the gray scale value of the display sub-area is equal to one of the multiple binding point gray scale values in the second preset compensation table, the display brightness value of the display sub-area is not equal to any one of the binding point display brightness values, or the display brightness value of the display sub-area is equal to one of the multiple binding point display brightness values in the second preset compensation table, the display gray scale value of the display sub-area is not equal to any one of the binding point gray scale values, or the display brightness value of the display sub-area is not equal to any one of the binding point display brightness values and the display gray scale value of the display sub-area is not equal to any one of the binding point gray scale values, the corresponding relationship between the display gray scale value and the correction coefficient of the display sub-area under the display brightness value is determined by interpolation according to the second preset compensation table.

[0163] S172: Determine the correction coefficient corresponding to the display sub-area according to the display brightness value of the display sub-area and the display gray scale value of the display sub-area, and the corresponding relationship between the display gray scale value and the correction coefficient under the display brightness value of the display sub-area. The display brightness values of the display sub-areas are the same.

[0164] The multiple sets of corresponding relationships between the different display gray scale values under different display brightness values and the correction coefficients are established in advance, that is, the second preset compensation table is established in advance. The corresponding relationship between the display gray scale value and the correction coefficient under the display brightness value of the display sub-area is determined by table lookup or interpolation, and then the correction coefficient corresponding to the display sub-area is determined.

[0165] S182: Correct the first compensation value of the display sub-area according to the correction coefficient of the display sub-area.

[0166] The product of the correction coefficient corresponding to the display sub-area and the first compensation value is taken as the final compensation value. For any sub-pixel in any display sub-area, the final compensated data voltage is generated according to the initial data voltage of the sub-pixel and the final compensation value, and the light emitting device of the sub-pixel is driven to display according to the final compensated data voltage. Each sub-pixel in each display sub-area is driven in the above similar manner to complete the brightness compensation of the second display area 2.

[0167] In this embodiment, the second display area is divided into multiple display sub-areas, and different display sub-areas correspond to different first compensation values. Compared with the case where the entire second display area corresponds to the same first compensation value, the compensation of the second display area is more precise, and the accuracy of the brightness compensation is improved.

[0168] Optionally, the display brightness value of the second display area is obtained before the brightness compensation of the real panel; the first compensation value of the second display area is determined according to the gray scale value of the second display area when the display brightness value is less than the display brightness threshold; wherein the preset display brightness value is less than or equal to the display brightness threshold. The brightness of the second display area is more obvious in low brightness, so the subsequent brightness compensation of the display panel can be performed only when the display brightness value is less than the display brightness threshold. The display brightness threshold is the maximum value of the brightness compensation of the second display area. For example, the brightness corresponding to the maximum gray scale at the display brightness threshold can be 10 nit. The brightness corresponding to the maximum gray scale at the preset display brightness value can be 2 nit. Since the brightness of the second display area is more obvious in low brightness, the first preset compensation table is established with a smaller preset display brightness value, so that the first compensation value is more accurate, and the brightness of the sub-pixel driven by the first compensation value is closer to the target brightness.

[0169] Optionally, the display panel comprises a gate drive circuit, the gate drive circuit is connected to a clock signal and a frequency cutting signal; the gate drive circuit is configured to output a scanning signal of a first frequency to the first display area and a scanning signal of a second frequency to the second display area according to the frequency cutting signal.

[0170] One driving period of the second display area comprises a holding frame and a refreshing frame. In the refreshing frame, the control clock signal is a pulse signal; in the holding frame, the control clock signal is an invalid potential; the invalid potential is a potential for turning off a transistor connected to the clock signal in the gate drive circuit; wherein the invalid potential is a direct current potential.

[0171] Specifically, the gate drive circuit can include a plurality of stages of shift registers arranged in cascade, each stage of shift registers corresponding to at least one row of sub-pixels, and each stage of shift registers being connected to a frequency switching signal, the frequency switching signal being used to control whether the shift register can output the input signal connected thereto as a scanning signal after shifting. Therefore, by controlling the potential change of the frequency switching signal, the scanning signal of the first frequency can be output to the first display area, and the scanning signal of the second frequency can be output to the second display area. The scanning signal is a signal for controlling the data writing transistor to be turned on or turned off. For example, the first display area is refreshed at 120HZ, and the second display area is refreshed at 1HZ. Therefore, one driving period can be considered as one second, in which the first display area is refreshed 120 times, and the second display area is refreshed only once. In one second, the display panel includes 120 frames, corresponding to the first display area, which is a refresh frame in the 120 frames, and each frame performs data voltage writing. The second display area includes only one refresh frame and 119 holding frames in the 120 frames, and the data voltage is written in the refresh frame, and the scanning signal controls the data writing transistor to be turned off in the holding frame. In order to reduce the power consumption of the display panel, the clock signal is controlled to be invalid potential in the holding frame of the low refresh area, i.e., the second display area, so as to avoid the waste of energy caused by the high and low potential switching of the clock signal. Figure 6 A structure diagram of a display panel provided by an embodiment of the present application is shown in FIG. 1. Figure 6 A plurality of sub-pixels 30 are arranged in an array in the display area AA of the display panel, and the gate drive circuit 100 is arranged in the non-display area NAA. The scanning lines LS extend along the row direction of the display panel 4. The display panel 4 further includes data lines LD extending along the column direction of the display panel 4, which are used to provide data voltage Vdata to each sub-pixel 30.

[0172] The gate drive circuit 100 comprises a plurality of shift registers 40 and a plurality of gating units 20; the gating unit 20 is connected to the corresponding shift register 40 and the scan line LS, and the gating unit 20 is connected to the frequency cutting signal C3. The plurality of shift registers 40 can be connected in cascade. The frequency cutting signal C3 is a global signal, and each gating unit 20 in the same gate drive circuit 100 is connected to the same frequency cutting signal C3. The gating unit 20 is used to control whether the gating unit 20 replicates and outputs the on pulse of the output signal GOUT of the shift register 40 according to the frequency cutting signal C3, so as to control the pulse frequency of the scan signal SCAN transmitted to the scan line LS. For the convenience of description, one scan line LS is connected to each gating unit 20, and the nth scan line LS is connected to the nth row of sub-pixels 30. The driving process of the gate drive circuit 100 in the multi-frequency display process is described by taking the third display area 3 of the display panel 1 as an example. The third display area 3 of the display panel 1 comprises the first to kth rows of sub-pixels 30, the first display area 1 comprises the k+1th to mth rows of sub-pixels 30, and the second display area 2 comprises the m+1th to ith rows of sub-pixels 30. The first frequency is 120HZ, and the second frequency is 1HZ. Specifically, the frequency cutting signal C3 can be kept in the on state in the display frame F1, so that the sub-pixels 30 in each display area are refreshed in the display frame. The display frame F1 is equivalent to the refresh frame of the first display area 1, the second display area 2 and the third display area 3. The output signal GOUT of each shift register 40 is an effective potential pulse, which is configured as the on pulse of the scan signal SCAN connected to the i rows of sub-pixels 30. In the subsequent n-1 display frames, the frequency cutting signal C3 is controlled to be in the off state corresponding to the second display area 2 and the third display area 3, and in the on state corresponding to the first display area 1. The sub-pixels 30 in the first display area 1 are refreshed in the display frames F2 to Fn, and the sub-pixels 30 in the second display area 2 and the third display area 3 are not refreshed in the second display frame to the nth display frame. N is 120.

[0173] Figure 7 A timing diagram of a clock signal is provided for the embodiment of the present application. The clock signal comprises a first clock signal CLK1 and a second clock signal CLK2. The timing of the first clock signal CLK1 is taken as an example in the first display frame F1. Both clock signals are pulse signals. In the subsequent n-1 display frames, such as the display frame F2 to the display frame Fn, only the display frame F2 is shown in the figure. Both clock signals are controlled to be in the DC state corresponding to the second display area 2 and the third display area 3, and in the pulse signal state corresponding to the first display area 1. Figure 6 and Figure 7 , Figure 7

[0174] ​In the maintaining frame, the control clock signal is lowered to the inactive potential to reduce the power consumption of the display panel, and because the data writing transistors of the first display area and the second display area are turned on and turned off different times in the same time, the second display area has the problem of display being too dark or too bright, so the brightness of the second display area is compensated by using the brightness compensation method of the display panel in any of the above embodiments.

[0175] Optionally, the display panel includes a plurality of rows of sub-pixel rows, each row of sub-pixel rows includes a plurality of sub-pixels, each row of sub-pixels is refreshed row by row, and the first display area and the second display area are arranged along the column direction of the sub-pixels, and the second display area is refreshed later than the first display area.

[0176] As shown in Figure 5 each row of sub-pixels in the display panel is refreshed row by row, the second display area 2 is located below the refreshing direction of the first display area 1, and the third display area 3 is also a low refreshing area, but the clock signal in the third display area 3 is maintained as a pulse signal to ensure that the output scan signal is input into the second display area, and the second display area is refreshed at a high frequency. The data writing transistor is connected to the source of the driving transistor, and the compensation transistor is connected between the gate and the drain of the driving transistor. The compensation transistor can be turned off in the maintaining frame to realize low-frequency display of the third display area 3. Therefore, the third display area 3 will not have the problem of display abnormality, and only the brightness of the second display area 2 needs to be compensated.

[0177] Optionally, after the first compensation value is modified according to the correction coefficient, the method further includes:

[0178] The brightness of each row of sub-pixels in the second display area is compensated according to the modified first compensation value. The second display area includes a plurality of rows of sub-pixel rows, and each row of sub-pixels can be modified according to the modified first compensation value. Specifically, each row of sub-pixels in the second display area corresponds to the same first compensation value, and further corresponds to the same modified first compensation value, or each row of sub-pixels corresponds to a first compensation value, or the second display area is divided into a plurality of display sub-areas, and each display sub-area corresponds to a first compensation value, which is not limited. The positions of the first display area and the second display area are bound, and the starting compensation position coordinates of the second display area are determined according to the ending position coordinates of the first display area. Optionally, the first display area and the second display area are arranged adjacent to each other; the brightness of each row of sub-pixels in the second display area is compensated from the (L+1)th row of sub-pixel rows; wherein the Lth row of sub-pixel rows is the latest refreshed row of sub-pixels in the first display area, and L is an integer greater than or equal to 1. For example, the first display area ends at the Lth row, and the brightness of each row of sub-pixels is compensated from the (L+1)th row, so that the compensation area is dynamically adjusted according to the refreshing area, and L is an integer greater than or equal to 1.

[0179] Alternatively, the second display area includes n rows of sub-pixel rows, n is an integer greater than or equal to 2, and after the first compensation value is modified according to the correction coefficient, the second display area further includes:

[0180] The L+mth row of sub-pixel rows in the display area of the display panel to the nth row of sub-pixel rows in the second display area are compensated in brightness according to the modified first compensation value; wherein the nth row of sub-pixel rows is the latest refreshed row of sub-pixel rows in the second display area, the Lth row of sub-pixel rows is the latest refreshed row of sub-pixel rows in the first display area, m is an integer greater than or equal to 2, L is an integer greater than or equal to 1, and m is less than or equal to n.

[0181] The positions of the first display area and the second display area are bound, and the starting compensation position coordinates of the second display area are determined according to the end position coordinates of the first display area. For example, the first display area ends at the hth row, and the brightness of the sub-pixels in each row of sub-pixel rows is compensated starting from the (h+m)th row. If the display area includes the first display area and the second display area, the first display area includes 50 rows of sub-pixels, the second display area includes 60 rows of sub-pixels, m=10, and the brightness of the 60th row of sub-pixels to the 60th row of sub-pixels in the second display area, i.e. the 110th row of sub-pixels in the entire display area, is compensated. Because the brightness of the sub-pixels in the 10 rows after the end of the first display area is less abnormal, the brightness of the sub-pixels in the remaining rows in the second display area except for the first 10 rows of sub-pixels can be compensated. Alternatively, the first display area and the second display area are connected to different gate drive circuits to refresh at different frequencies. Optionally, the display panel includes at least a first gate drive circuit for outputting a scanning signal of a first frequency to the first display area and a second gate drive circuit for outputting a scanning signal of a second frequency to the second display area, and the first gate drive circuit and the second gate drive circuit are connected to different clock signals; one driving period of the second display area includes a holding frame and a refreshing frame, and in the refreshing frame, the clock signal connected to the second gate drive circuit is controlled to be a pulse signal; in the holding frame, the clock signal connected to the second gate drive circuit is controlled to be an invalid potential; the invalid potential is a potential that turns off the transistor connected to the clock signal in the gate drive circuit, and the invalid potential is a direct current potential. The clock signal connected to the second gate drive circuit is maintained at an invalid potential in the holding frame of the second display area to reduce the power consumption of the display panel, and at the same time, the gate drive circuit has no scanning signal output in the holding frame, and the data writing transistor is in an off state, so that the second display area is refreshed at a second frequency. Because different display areas correspond to different gate drive circuits, the main problem of low refresh rate areas is that there may be display abnormalities. At this time, the brightness of the sub-pixels in the second display area is compensated according to the first compensation value modified according to the correction coefficient. Figure 5 The second display area 2 and the third display area 3 in the middle can be compensated in brightness.

[0182] Optionally, the display area of the display panel at least includes a first display area and a second display area, and the display panel further includes a gate drive circuit, which is connected to a clock signal and a frequency division signal; the gate drive circuit is configured to output a scanning signal with a first frequency to the first display area and a scanning signal with a second frequency to the second display area according to the frequency division signal; and the first frequency is greater than the second frequency.

[0183] The brightness compensation method of the display panel includes:

[0184] According to the display data of the second display area, a display compensation value of the second display area is determined; the display data includes a gray scale value and / or a display brightness value; and the display compensation value includes a gray scale compensation value or a data voltage compensation value.

[0185] In the hold frame, after the clock signal is controlled to be at an inactive potential to reduce the power consumption of the display panel, the data writing transistors of the first display area and the second display area are turned on and turned off at different times, so that the second display area appears to be dark or bright, and thus the brightness of the second display area needs to be compensated to solve the display abnormality of the second display area.

[0186] The embodiment of the present application further provides a brightness compensation device of a display panel, Figure 8 A structural schematic diagram of the brightness compensation device of the display panel provided by the embodiment of the present application is shown in Figure 8 The display area of the display panel at least includes a first display area and a second display area,

[0187] The brightness compensation device of the display panel includes:

[0188] The first compensation value generation module 10 is configured to determine a first compensation value according to a gray scale value of the second display area when the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency; and the first frequency is greater than the second frequency.

[0189] The correction coefficient generation module 11 is configured to determine a correction coefficient according to a display brightness value and a gray scale value of the second display area.

[0190] The brightness correction module 12 is configured to correct the first compensation value according to the correction coefficient.

[0191] The brightness compensation device of the display panel has the same beneficial effects as the brightness compensation method of the display panel, and thus will not be described here.

[0192] The embodiment of the present application further provides a display device, Figure 9 A structural schematic diagram of the display device provided by the embodiment of the present application is shown in Figure 9The display device includes the brightness compensation device of the display panel described above, and the display device 13 can be a mobile phone as shown in the figure, a computer, a television, a smart wearable display device, etc., and the embodiments of the present application do not specially limit this. Figure 9

[0193] It should be understood that the various forms of flow shown above can be used to reorder, add or delete steps. For example, each step described in the present application can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, and the present application is not limited herein.

[0194] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.​

Claims

1. A method for luminance compensation of a display panel, characterized in that, The display area of the display panel comprises at least a first display area and a second display area, and the brightness compensation method of the display panel comprises: when the first display area is refreshed at a first frequency and the second display area is refreshed at a second frequency: determining a first compensation value of the second display area according to a gray scale value of the second display area; determining a correction coefficient according to a display brightness value and a gray scale value of the second display area; correcting the first compensation value according to the correction coefficient; wherein the first frequency is greater than the second frequency; determining the first compensation value of the second display area according to the gray scale value of the second display area and a corresponding relationship between the gray scale value and the first compensation value of the second display area; the driving chip corresponding to the display panel comprises a gamma circuit, and the gamma circuit is used for outputting a gamma voltage; determining the first compensation value of the second display area according to the gray scale value of the second display area and a corresponding relationship between the gray scale value and the first compensation value of the second display area; determining a first compensation coefficient corresponding to the second display area according to the gray scale value of the second display area and a corresponding relationship between the gray scale value and the first compensation coefficient of the second display area; and performing operation on the first compensation coefficient corresponding to the second display area, a gamma pressure difference value and the accuracy of the gamma circuit to obtain the first compensation value of the second display area, wherein the gamma pressure difference value is a difference between a maximum value and a minimum value of the gamma voltage output by the gamma circuit. determining the correction coefficient according to the display brightness value and the gray scale value of the second display area and a corresponding relationship between the gray scale value and the correction coefficient under the display brightness value of the second display area. 2.The brightness compensation method of a display panel according to claim 1, wherein, The first compensation value of the second display area is a product of the first compensation coefficient and a gamma step length, and the gamma step length is a ratio of the gamma pressure difference value to the accuracy of the gamma circuit. correcting the first compensation value according to the correction coefficient comprises:

3. The brightness compensation method of a display panel according to claim 2, wherein, taking a product of the correction coefficient and the first compensation value as a corrected compensation value.

4. The brightness compensation method of a display panel according to claim 3, wherein, The second display area comprises a plurality of display sub-areas, and determining the first compensation value of the second display area according to the gray scale value of the second display area and a corresponding relationship between the gray scale value and the first compensation value of the second display area comprises: for any display sub-area in the second display area:

5. The brightness compensation method of a display panel according to claim 2, wherein, determining a first compensation coefficient corresponding to the display sub-area according to a gray scale value of the display sub-area and a corresponding relationship between the gray scale value and the first compensation coefficient of the display sub-area; performing operation on the first compensation coefficient corresponding to the display sub-area, a gamma pressure difference value and the accuracy of the gamma circuit to obtain a first compensation value of the display sub-area; determining the correction coefficient according to the display brightness value and the gray scale value of the second display area comprises: determining the correction coefficient according to the display brightness value and the gray scale value of the display sub-area. ​ ​ 6. The brightness compensation method of a display panel according to claim 5, wherein, Before the determining the first compensation coefficient corresponding to the second display area according to the gray scale value of the second display area and the corresponding relationship between the gray scale value of the second display area and the first compensation coefficient, the method further comprises: obtaining a first preset compensation table, wherein the first preset compensation table comprises a plurality of binding point gray scale values and a first compensation coefficient corresponding to each display sub-area at each binding point gray scale value; for any display sub-area: when the gray scale value of the display sub-area is equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined from the first preset compensation table by table lookup; when the gray scale value of the display sub-area is not equal to any one of the binding point gray scale values, the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient is determined according to the first preset compensation table and by interpolation.

7. The brightness compensation method of a display panel according to claim 5, wherein determining the correction coefficient corresponding to the second display area according to the display brightness value and the gray scale value of the second display area, and the corresponding relationship between the gray scale value under the display brightness value of the second display area and the correction coefficient comprises: for any display sub-area: determining the correction coefficient corresponding to the display sub-area according to the display brightness value of the display sub-area and the gray scale value of the display sub-area, and the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient; wherein the display brightness values of each display sub-area are the same; before the determining the correction coefficient corresponding to the display sub-area according to the display brightness value of the display sub-area and the gray scale value of the display sub-area, and the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient, the method further comprises: obtaining a second preset compensation table, wherein the second preset compensation table comprises a plurality of binding point display brightness values, a plurality of binding point gray scale values, and a correction coefficient corresponding to the binding point gray scale value under the binding point display brightness value; wherein each display sub-area corresponds to the same second preset compensation table; when the gray scale value of the display sub-area is equal to any one of the binding point gray scale values and the display brightness value of the display sub-area is equal to any one of the binding point display brightness values, the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient is determined from the second preset compensation table by table lookup; when the gray scale value of the display sub-area is not equal to any one of the binding point gray scale values and / or the display brightness value of the display sub-area is not equal to any one of the binding point display brightness values, the corresponding relationship between the gray scale value under the display brightness value of the display sub-area and the correction coefficient is determined according to the second preset compensation table by interpolation. 8.The brightness compensation method of the display panel according to claim 6, characterized in that, under different division modes of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division modes corresponds to the same first preset compensation table.

9. The brightness compensation method of a display panel according to claim 6, wherein, under different division modes of dividing the display panel into at least a first display area and a second display area, the second display area corresponding to different division modes corresponds to different first preset compensation tables; Before the determining the first compensation coefficient corresponding to the display sub-area according to the gray scale value of the display sub-area and the corresponding relationship between the gray scale value of the display sub-area and the first compensation coefficient, the method further comprises: establishing a plurality of test groups, the test groups comprising a first display area and a second display area, the positions of the first display area and the second display area being different in different test groups; establishing a plurality of refresh frequency groups, the refresh frequency groups comprising a first frequency and a second frequency; for any test group, establishing a corresponding first compensation table of the test group under each refresh frequency group; determining the test group to which the first display area and the second display area belong according to the positions of the first display area and the second display area in the display panel; determining the first preset compensation table according to the corresponding first compensation table of each refresh frequency group under the test group, the first frequency and the second frequency.

10. The brightness compensation method of a display panel according to claim 9, wherein, For any test group, establishing a corresponding first compensation table of the test group under any refresh frequency group comprises: selecting m gray scale values from a plurality of gray scale values as binding point gray scale values; m is an integer greater than or equal to 2; refreshing the first display area of the test display panel at the first frequency and refreshing the second display area of the test display panel at the second frequency; for any of the binding point gray scale values: lighting the second display area at the binding point gray scale value under a preset display brightness value, and collecting the actual brightness of each display sub-area in the second display area; generating a first compensation coefficient of each display sub-area according to the actual brightness of each display sub-area and the target brightness corresponding to the binding point gray scale value under the preset display brightness value; generating the first compensation table according to the first compensation coefficient corresponding to each display sub-area under each binding point gray scale value.

11. The brightness compensation method of a display panel according to claim 7, wherein, Generating the second preset compensation table comprises: selecting h binding point display brightness values from a plurality of display brightness values; h is an integer greater than or equal to 2; for any display sub-area and any binding point display brightness value, generating a second compensation coefficient corresponding to the binding point gray scale value under the binding point display brightness value according to the compensated brightness corresponding to the first compensation value and the target brightness corresponding to the binding point gray scale value of the display sub-area under the binding point display brightness value under any binding point gray scale value; taking the second compensation coefficient corresponding to any display sub-area satisfying a preset condition as a correction coefficient; the preset condition is that the absolute value of the difference between the first brightness of each display sub-area and the target brightness corresponding to the binding point gray scale value under the binding point display brightness value is less than the absolute value of the difference between the second brightness and the target brightness corresponding to the binding point gray scale value under the binding point display brightness value; the first brightness is the brightness of the display sub-area when lighting at the data voltage generated by the first compensation value; the second brightness is the brightness of the display sub-area when lighting at the data voltage generated by correcting the first compensation value according to the second compensation coefficient; If there is no second compensation coefficient satisfying the preset condition at the display brightness value of the binding point gray scale value, the correction coefficient corresponding to the display brightness value of the binding point gray scale value is set to 1.

12. The brightness compensation method of a display panel according to claim 10, wherein, Before the first compensation value of the second display area is determined according to the gray scale value of the second display area, the method further comprises: obtaining a display brightness value of the second display area; when the display brightness value is less than a display brightness threshold value, determining the first compensation value of the second display area according to the gray scale value of the second display area; wherein the preset display brightness value is less than or equal to the display brightness threshold value.

13. The method of claim 1, wherein, The display panel comprises a gate drive circuit, and the gate drive circuit is connected to a clock signal and a frequency division signal; the gate drive circuit is configured to output a scanning signal of a first frequency to the first display area and a scanning signal of a second frequency to the second display area according to the frequency division signal; one driving period of the second display area comprises a holding frame and a refreshing frame, in the refreshing frame, the clock signal is controlled to be a pulse signal; in the holding frame, the clock signal is controlled to be an invalid potential; the invalid potential is a potential for turning off a transistor connected to the clock signal in the gate drive circuit; wherein the invalid potential is a direct current potential.

14. The brightness compensation method of a display panel according to claim 13, wherein, The display panel comprises a plurality of sub-pixel rows, each sub-pixel row is refreshed row by row, the first display area and the second display area are arranged along the column direction of the sub-pixels, and the second display area is refreshed later than the first display area.

15. The brightness compensation method of a display panel according to claim 14, wherein, After the first compensation value is corrected according to the correction coefficient, the method further comprises: performing brightness compensation on each sub-pixel row in the second display area according to the corrected first compensation value.

16. The brightness compensation method of a display panel according to claim 15, wherein, The first display area and the second display area are arranged adjacently; brightness compensation is performed on each sub-pixel row in the second display area starting from the L+1th sub-pixel row; wherein the Lth sub-pixel row is the latest refreshed sub-pixel row in the first display area, and L is an integer greater than or equal to 1.

17. The method of brightness compensation of a display panel according to claim 14, wherein, The second display area comprises n sub-pixel rows, n is an integer greater than or equal to 2, and after the first compensation value is corrected according to the correction coefficient, the method further comprises: performing brightness compensation on the L+mth sub-pixel row to the nth sub-pixel row in the second display area of the display panel according to the corrected first compensation value; wherein the nth sub-pixel row is the latest refreshed sub-pixel row in the second display area, the Lth sub-pixel row is the latest refreshed sub-pixel row in the first display area, m is an integer greater than or equal to 2, L is an integer greater than or equal to 1, and m is less than or equal to n.

18. The method of brightness compensation of a display panel according to claim 1, wherein, The display panel comprises at least a first gate drive circuit for outputting a scanning signal of a first frequency to the first display area and a second gate drive circuit for outputting a scanning signal of a second frequency to the second display area, and the first gate drive circuit and the second gate drive circuit are connected to different clock signals; One driving period of the second display area includes a holding frame and a refreshing frame, in the refreshing frame, the clock signal accessed by the second gate driving circuit is a pulse signal; in the holding frame, the clock signal accessed by the second gate driving circuit is an invalid potential; the invalid potential is a potential for turning off the transistor in the gate driving circuit which accesses the clock signal; wherein the invalid potential is a direct current potential.

19. A luminance compensation device of a display panel, characterized by comprising: The driving chip corresponding to the display panel comprises a gamma circuit, the gamma circuit is used for outputting a gamma voltage, and the display area of the display panel at least comprises a first display area and a second display area, The brightness compensation device of the display panel comprises: A first compensation value generation module is configured to, when refreshing the first display area at a first frequency and refreshing the second display area at a second frequency, determine a first compensation coefficient corresponding to the second display area according to a gray scale value of the second display area and a corresponding relationship between the gray scale value of the second display area and the first compensation coefficient, and perform operations on the first compensation coefficient corresponding to the second display area, a gamma pressure difference value, and the accuracy of the gamma circuit to obtain a first compensation value of the second display area; the gamma pressure difference value is the difference between the maximum value and the minimum value of the gamma voltage output by the gamma circuit; wherein the first frequency is greater than the second frequency; A correction coefficient generation module is configured to determine a correction coefficient according to a display brightness value and a gray scale value of the second display area; A brightness correction module is configured to correct the first compensation value according to the correction coefficient.

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